JP2794432B2 - Exhaust gas pretreatment agent - Google Patents

Description

The present invention relates to an exhaust gas pretreatment agent for removing gaseous catalyst poisons in an exhaust gas contact treatment method.

(Prior art)

2. Description of the Related Art Conventionally, a method of catalytically treating harmful components in exhaust gas using a catalyst has been widely used as one of methods for preventing air pollution and removing odors. If the catalyst used in the exhaust gas contact treatment method contains dust, tar, carbon, organometallic compounds, silicone compounds, phosphorus compounds, etc. in the exhaust gas, the active function of the catalyst is inhibited and stable for a long time It was difficult to maintain the function.

Solid or liquid dust contained in exhaust gas,
Most of carbon, tar, etc. can be removed by existing filters, cyclones, scrubbers, etc., but it is extremely difficult to effectively remove catalytic poisons such as gaseous organic metal components, silicon compounds, and organic phosphorus compounds. Was.

In order to remove these gaseous catalyst poisons, activated carbon (Japanese Patent Publication No. 56-41299) silica gel (Japanese Patent Publication No.
6-9126) A method of pretreating exhaust gas with alumina (JP-A-55-15622) has been used.

[Problems to be solved by the invention]

The pretreatment agents used in the conventional pretreatment agent methods as described above have problems in terms of usable temperature, removal effect, service life, and the like. That is, in the activated carbon treatment, there is a risk of ignition and the use is restricted for safety. In addition, silica gel and alumina do not always have a sufficient active life, and there has been a demand for a pretreatment agent which has a higher pretreatment effect, has a longer active life, and is not restricted by handling.

[Means and actions for solving the problems]

The present inventors have conducted intensive studies to meet the above-mentioned demands, and as a result, have found that active manganese oxide removes the gaseous catalyst poison extremely efficiently over a long period of time.

Further, by supporting the active oxygen manganese on a carrier, pressure loss can be improved and handling can be simplified, so that the apparatus can be made more compact.

As the carrier, a porous inorganic carrier having a high surface area is desirable, and alumina, silica, magnesia, titania,
Zirconia, cordierite, mullite and the like are used. Among them, activated alumina having a large surface area is desirable.

As the shape of the carrier, any of pellets, tertiary network structures, honeycomb structures, fiber aggregates and the like can be used, but among them, a three-dimensional network structure having a low pressure loss and easy handling is preferable, and a honeycomb structure and the like are preferable. More preferably, a honeycomb structure formed of a sheet-like aggregate of ceramic fibers selected from inorganic fibers such as silica fibers, alumina fibers, aluminosilicate fibers, and zirconia fibers bonded to each other by a silicate gel, It has pores between fibers having a diameter of 5000 mm or more effective for gas diffusion of 0.1 cc / g or more, preferably 0.2 cc / g, which is desirable because active manganese oxide can be uniformly and highly dispersed and supported in a large amount.

Active manganese oxide is supported on the above-described carrier by a conventional method, and then dried and calcined to obtain a desired catalyst. Active manganese oxide carrying amount is 20 g / or more in terms of Mn, particularly preferably 70 to 90 g /.
Is desirable.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 Nichias Co., Ltd. trade name “Honeycle” carrier (205 cells / square inch, porosity 80%, which is a honeycomb structure composed of sheet-like aggregates in which alumina-silica-based ceramic fibers are bonded to each other by silica gel) ABD, 0.20g / c
m ³⁾ to 15.8 wt% of manganese nitrate in terms of Mn [Mn (NO _{3) 2}
· 6H ₂ O] it was immersed in an aqueous solution of, the excess aqueous solution after pulling attaching 60 g / manganese nitrate in terms of Mn blown with air to a carrier.

The carrier with manganese nitrate is dried with heated air to remove excess water and water of crystallization sufficiently, and then heated to a temperature of 200 to 400 ° C. to decompose manganese nitrate into activated manganese oxide having a black appearance and pre-treat. Agent A was obtained.

COMPARATIVE EXAMPLE 1 Using the same "honeycle" carrier as in Example 1, the carrier was wash-coated with an alumina slurry containing 20% by weight of γ-alumina, and the excess slurry was blown off with air to remove 100 g / alumina. Is carried. After the wash-coated carrier was dried, it was calcined at a temperature of 550 ° C. to obtain the treating agent B.

Next, the test apparatus used in the present invention will be described with reference to FIG. A predetermined amount of a solution obtained by adding a catalyst poison to a solvent was mixed into the air from the line 1 from the line 2 to prepare a test gas.

The concentration of the catalyst poison in the test gas was set higher than a general one, so that the effect of the pretreatment agent could be judged in a short time.

The test gas is heated to a predetermined temperature by the electric heater 3 and introduced into the pretreatment agent layer 4 and the catalyst layer 5 filled with the pretreatment agent, and catalytic oxidation of the solvent contained in the test gas is performed.

Test Example 1 A test gas containing about 500 ppm of methyl ethyl ketone to which gaseous dimesyl silicone (5 ppm in terms of Si) was added as a catalyst poison using the above-described test apparatus at a temperature of 300 ° C. and a space velocity (SV value) of 70,000 hr ⁻ The change in the reaction rate of methyl ethyl ketone due to the catalyst when passing through ¹ was measured, and the results are shown in FIG.

 In addition, the thickness of the pretreatment agent layer was subjected to an 80 mm test.

〔The invention's effect〕

As is clear from the above description, the pretreatment agent of the present invention has a better pretreatment effect than the conventional pretreatment, and has an excellent effect of exhibiting durability performance of maintaining the pretreatment agent effect significantly longer. To play.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a test apparatus used in the present invention, and FIG.
The figure is a characteristic diagram showing the relationship between the catalyst reaction rate (%) and time. 4: Pretreatment agent 5: Catalyst layer

Claims (3)

(57) [Claims] An exhaust gas pretreatment agent comprising active manganese oxide for removing at least one gaseous catalyst poison selected from an organic metal compound, a silicone compound and an organic phosphorus compound. 2. The exhaust gas pretreatment agent according to claim 1, wherein said active manganese oxide is carried on a honeycomb carrier comprising at least one inorganic material selected from alumina, silica, titania and cordierite. . 3. The honeycomb carrier is composed of a sheet-like aggregate of at least one type of ceramic fiber selected from silica fibers, alumina fibers, aluminosilicate fibers, and zirconia fibers bonded to each other by a silica gel. The pretreatment agent for exhaust gas according to claim 2, wherein